1. Field of the Invention
The present invention relates to a drive belt for use in a V-belt continuously variable transmission. More specifically, the present invention relates to a drive belt that is capable of accommodating the off-centering of the pulleys in the axial direction.
2. Background Information
An example of a typical V-belt for a continuously variable transmission is shown in Japanese Laid-Open Patent Publication No. 8-21488. This V-belt continuously variable transmission basically includes an assembled power transmission V-belt that runs between the V-shaped groove of an input pulley and the V-shaped groove of an output pulley. The input pulley is driven so as to rotate about a first axis, while the output pulley rotates about a second axis that is parallel to the first axis. In this arrangement, the rotation of the input pulley is transmitted to the output pulley via the assembled power transmission V-belt. During this transmission, the movable flanges of both pulleys are moved in the axial such that the movable flanges move either closer to or farther away from the stationary flanges. As a result, the arc radius of power transmission V-belt where it wraps around the input and output pulleys varies in a continuous manner such that continuously variable gear changing can be accomplished.
This assembled power transmission V-belt is equipped with a plurality of the V-shaped blocks having slanted end surfaces that frictionally contact the side walls of the V-shaped grooves of the pulleys. These V-shaped blocks are arranged successively in an endless shape so as to form a V-shaped drive belt. The ends of the V-shaped blocks have shoulder parts with a pair of endless bands resting thereon. Each of the endless bands comprises a plurality of endless band elements (rings) layered on top of one another in the radial direction. The assembled power transmission V-belt is utilized as previously described by running the endless arrangement of the V-shaped blocks between the V-shaped grooves of the input and output pulleys.
In view of the above, there exists a need for an improved drive belt. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.
It has been discovered that in a V-belt continuously variable transmission, as described in the aforementioned publication, the displacement of the center planes of the V-shaped grooves that occurs during the axial movements of the moveable flanges do not match when moveable flanges are moved in the same axial direction during gear changing control. At some power transmission ratios, the two center planes of the pulleys are aligned. However, at other power transmission ratios, the center planes of the pulleys are offset from each other in the axial direction by a distance xcex1 (so-called xe2x80x9coff-centerxe2x80x9d condition). Thus, the V-shaped blocks that rest on input pulley and the V-shaped blocks that rest on output pulley are off-center from each other.
It has further been discovered that a conventional power transmission V-belt has high rigidity in the axial direction and only allows a small amount of axial deflection when off-centering occurs because the endless band is constructed from a plurality of endless band elements layered on top of one another in the radial direction. Consequently, a transverse force acts on the V-belt such that the entire V-belt becomes slanted with respect to a line perpendicular to the rotational axes of the pulleys. Moreover, this transverse force causes the V-shaped blocks becomes tilted with respect to the pulleys, since the V-shape blocks are unable to maintain their parallel orientation with respect to the pulley axes. The durability of the pulleys and the V-shaped blocks should be improved in order to withstand this behavior.
If the endless band were made from an elastic material, the allowable axial deflection would be increased and it would be easier for the V-shaped blocks to maintain their parallel orientation with respect to the pulley axis. However, the rigidity of the belt in the lengthwise direction (circumferential direction) would decline and there would be a higher likelihood of increased vibrations and/or derailing of the V-shaped blocks during rotation.
One object of the present invention is to improve the durability of a power transmission belt by making it easy for the V-shaped blocks to maintain their parallel orientation with respect to the rotational axes of the pulleys and preventing the V-shaped blocks from becoming tilted with respect to the pulleys when the amount of off-centering is large.
In order to achieve this object, a drive belt is provided for use in a continuously variable transmission having a V-shaped pulley with ring aggregates made by laminating a plurality of endless rings in both the radial and axial directions. The drive belt comprises an endless carrier and a plurality of elements. The endless carrier comprises a plurality of first endless metal belts with plank-shaped cross sectional shapes laminated together in both radial and axial directions to form a first ring aggregate. The plurality of elements are supported on the endless carrier and aligned in a peripheral direction of the endless carrier to contact each other. The elements have a pair of tapered side surfaces adapted to move in conjunction with a pulley surface of the V-shaped pulley.
These and other objects, features, aspects and advantages of the present invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses a preferred embodiment of the present invention.